Comprehensive Description

Description

"Gennadas kempi, n. sp.

Plate XXVII

In spite of its mutilated condition, the specimen here described seems properly separable from other known species. It makes a near approach to G. elegans in the outlines of the carapace, in the proportions of the third peraeopod, and in having only one pair of spines at apex of the strongly sulcate telson. But there are several differences. The second joint of the first antennae is not shorter than the third. The scale of the second antennae is produced well beyond the little lateral tooth. The curved spines behind the narrow apical process of the endopod in the second maxilla are four in number, two much more curved than the others. In the first maxilliped the exopod is shorter instead of longer than the endopod. The petasma is nearer to that of G. calmani, Kemp, than any other that has been figured, but is more truncate; the inner opposed margins are straight, lined with a multitude of little coupling hooks. The first pleon segment is ventrally produced to a sharp point, and in G. calmani it is said to carry "a very strong, sharply pointed spine," which may mean the same thing. The apex of the telson is truncate, not rounded, with five plumose setae between the single pair of spines, as in G. bouvieri, Kemp. G. calmani has (whether invariably or not is uncertain) eleven setae between two pairs of spines, subject to the variation of a single pair. It agrees with our species in the four curved spines of the second maxilla, but differs in the longer exopod of the first maxilliped. Both species belong to the group which have the fourth joint of the third peraeppod longer than the fifth, and in both the fingers of the chela in that limb are subequal to the palm, but in G. calmani the chela is half as long as the fifth joint, whereas in the new species it is more than half as long. Other differ­ences between these closely connected species will be found in the two pairs of antennae. In the first pair G.calmani has the second joint not equal to the third, but " fully three-quarters the length" of it; in the second pair the scale is scarcely at all produced beyond the lateral tooth. Through the condition of the respective specimens many features are not available for comparison. As described and figured by BATE for his G.parvus, the second pleopods have at the apex of the peduncle on the inner side two membranous leaf-like appendages. In BATE'S figure these show setules on the outer margin distally. In our species one of these is somewhat bean-shaped, without any armature; the other, lying between it and the endopod, is oval, having much of its inner and distal margin fringed with little, somewhat curved, spinules. One of the stations at which G. parvus was obtained by the Challenger was in lat. 37° 49’ N., long. 166° 37’ W., mid ocean, North Pacific, trawled from the reputed depth of 3050 fathoms, which, as will be seen, exceeds that assigned to the Scotia species, here named out of respect to Mr STANLEY KEMP."